Ch 29: Fungi

What are the characteristics of all fungi?

• Eukaryotic: Unicellular and multicellular (branching networks of multicellular filaments)

• Heterotrophs: Carbon and Energy from other organisms (living or dead organic matter)

• All use Alternation of generations

What are the ways fungi can be heterotrophs?

• Decomposers

• Parasitic (+/-) - diseases in animals, plants, parasite insects

• Mutualism (+/+)

Why are fungi being decomposers so important to the global carbon cycle?

Basically, along w/ a few bacteria, fungi are the only organisms that can digest wood completely. If this process does not occur, carbon remains trapped in wood. Without fungi, carbon dioxide would be tied up and unavailable for photosynthesis and the presence of undecayed organic matter would reduce the space available for plants to grow

What are some of the mutualistic relationships found in fungi?

• Roots of most land plants are colonized by an array of mutualistic fungi that provide water and key nutrients (nitrogen, phosphorus) to the host plant 

• Fungi living inside the shoots of certain plants help ward off herbiovers bymaking toxic compounds 

• Many insects harbor single-celled fungi in their guts that aid their digestion of plant material 

Fill in the Blank: Fungi that live in close association are said to be _________ and fungi along with the roots they are associated with are called ______

Mycorrhizal

Mycorrhizae

What are fungi that make their living by digesting dead plant material?

Saprophytes

What are the chemicals secreted by soil fungi which inhibit the growth of bacteria?

Antibiotics

What are the morphological traits of fungi?

• Their simple bodies

• Presence of Hyphae in Mycelia

• Type of reproductive structure

• Type of Reproduction

• Fungi’s close tie to animals

What are the two growth forms of fungi?

• Yeasts - single-celled fungi

• Mycelia - multicellular, filamentous structures

Mycelia: What are hyphae?

Long, narrow filaments that make up a mycelium

Mycelial Hyphae: In most terrestiral fungi, each filament is divided into cells by cross wall called…..

Septa

Mycelial Hyphae: What are the significance of pores in separate hyphae?

• Pores – gaps that enable a wide variety of materials even nuclei and other organelles to flow from one cell-like compartment to the next 

True or False: Hyphae can be coenocytic, which means filaments are not divided into separate cells and lack septa entirely, which can have hundreds or thousands of nuclei scattered throughout the mycelium

True

True or false: Mycelia have a large surface area which makes mycelia very thin and can cause it to dry quickly

True

True or False: Since mycelia is so thin, it always dries out

False; mycelia fungi produce reproductive cells called spores that are resistant to drying, so spores can endure dry periods and then germinate to form a new mycelium when conditions improve

What is also true about fungi?

• Mycelial growth is dynamic, changing w/ moisture availability and food supply

• Mycelia support external digestion and the absorptive lifestyle of fungi

What are the 4 ways sexual reproduction can occur in fungi?

• Swimming gametes and spores

• Zygosporangia

• Basidia

• Asci

Sexual Reproduction: What are chytrids?

• Species w/ swimming gametes/spores

• In water/wet species, the gametes or spores produced during sexual reproduction have flagella 

• These are the only motile cells known in fungi 

Sexual Reproduction: What are zygomycetes?

• Haploid hyphae from 2 individuals meet and become joined, cells from yoked hyphae fuse to form a distinctive spore-producing structure (zygosporangium) 

• Known as zygomycetes 

Sexual Reproduction: What are basidiomycetes, or club fungi?

• Mushrooms (etc) form specialized club-shaped cells at the ends of hyphae called basidia and each basidium produces four spores by meiosis

Sexual Reproduction: What are asci, or sac fungi?

• when fungi form specialized sac-like cells called asci at the tips of hyphae, and w/i each ascus, meiosis and one round of mitosis produces 8 spores 

How does asexual reproduction happen in fungi?

Asexual spores called conidia and conidia can be dispersed by water or wind currents and grow into new hyphae when conditions are right 

What are the 3 key traits that link animals and fungi?

• Many animals and most fungi synthesize the tough structural material called chitin (Chitin is a prominent component of the cell walls of fungi) 

• The flagella that develop in chytrid spores and gametes are similar to those observed in animals 

• Both animals and fungi store food by synthesizing glycogen (both are heterotrophic) 

How does alternation of generations work in fungi?

Key Lineages of Fungi: Microsporidia Characteristics

• Known Species: 1500 

• Absorptive Life Style: all are parasites of animal's cells, especially in insects or fish, where the fungi enter the host cell through a polar tube which microsporidian shoots into host cell 

• Life Cycle: Some appear to reproduce only asexually while others produce various types of sexual spores (Some infect several hosts to complete the life cycle) 

• Common examples: Many species can infect humans but only do damage on immuno-compromised victims, pests in honeybee/silkworm colonies

Key Lineages of Fungi: Chytrids Characteristics

• Habitat: Aquatic, common in fresh water 

• Known Species: 750 

• Absorptive Life Style: Many decompose plants by digesting cellulose, while others have mutualistic relationships in guts of some animals to help plant digestion, and some are parasitic which infect many animals and plants 

• Life Cycle: the only fungi that produces motile cells (both their spores/gametes swim w/ flagella) and most exhibit alternation of generations 

• Common examples: Batrachochytrium Dendrobatidis – disease caused by the fungus which infects frogs/amphibians 

Key Lineages of Fungi: Zygomycetes Characteristics

• Habitat: Food molds 

• Know Species: 1050 

• Absorptive Life Style: Many are saprophytes and live on plant debris, some are parasites on fungi, insects, or spiders 

• Life Cycle: Asexual reproduction commonly used by have asexual sporangia that produce spores but sexual reproduction can happen through the fusion of hyphae and formation of zygosporangium and sexual sporangia 

• Common Examples: Bread, soft fruit molds 

Key Lineages of Fungi: Glomeromycetes Characteristics

• Known Species: 200 

• Absorptive Lifestyle: Form mutualistic associations w/ plant roots in the form of arbscular mycorrhizal fungi (AMF) 

• Life Cycle: Most produce large spores but reproduction is difficult to grow and study, like as sexual reproduction has not be observed yet 

• Common Examples: AMFs contact plasma membranes of root cells, and many other play large roles in the ecology of prairies and tropical forests 

Key Lineages of Fungi: Basidiomycota Characteristics

• Known Species: 32000 

• Absorptive Lifestyle: Decompose wood by producing lignin peroxidase; some form ectomycorrhizal associations w/ tree roots; smut and rust fungi are plant parasites 

• Life Cycle: Produce haploid spores in club-shaped basidia; basidia of mushroom-forming species live in gills found under the cap 

• Common examples: Mushrooms, puffballs, brackets 

What are the fruiting bodies in basidiomycotas?

Basidium

Key Lineages of Fungi: Ascomycota Characteristics

• Known Species: 64000 

• Absorptive Life Style: Many form ectomycorrhizal associations w/ tree roots; some form mutualistic associations w/ photosynthetic algae or bacteria in lichens; some are predatory on protists or nematodes 

• Life Cycle: Produce haploid spores in sac-like asci; asci of many species found of fleshy, cup-shaped structures; many use asexual reproduction 

• Common Examples: Lichens are often sensitive to air pollution and are used as bioindicators, yeasts, penicillin  

• Morels – fruiting body, above ground fungal portion 

• Truffles – associated w/ roots of particular tree species (mutualistc mycorrhizae) and their fruiting bodies are attached to belowground mycelium, give off odors attracted to some animals, horrible for farmers 

• Blights, mildews, ergot, insect pathogens